Hey Guys... So I just bought a Canon XH A1 and love it so far. I shot my first wedding and of course, the reception was poorly lit...I did the mistake of setting my camera to Auto Gain...and the footage turned out really grainy. So I'm thinking of switching off the Auto Gain and using the manual gain switch.... am I correct in doing that? and any tips or hints would be great..I want to film a low light reception without grain.

Using auto gain is the same as using auto iris or auto shutter - a real no-no in pretty much any movie-making situation. You've found out pretty quickly which you should see as a good thing - though your current clients might not view it this way.

First thing you need to learn is that dimly-lit weddings mean you should stay at wide-angle and limit your gain-up to +9dB. And get yourself one of these 160 LED lamps - they're cheap and light (!) and will run off rechargeable AAs for hours. Wouldn't be without mine.

Personally I don't go above +6db gain. You can use the camera menu options to assign gain values to the manual gain switch - mine is currently L = +0db M = +3db H = +6db (some like to set L to -3db).

Remember you can always raise gain/gamma/brightness levels in post. Whether you use in-camera gain or tweak later you should consider applying a degree of simple picture softening to reduce the dancing pixels (or look at the Neat Video plugin which receives favourable reviews).

Better than applying any gain in some low-light situations is reducing shutter speed. For PAL this means stepping down from the normal 1/50 to 1/25. Lots more light and no added grain, but it depends on your situation - for subjects with little movement (i.e. speeches) you should be OK, but with moving subjects (such as dancing) or any real necessary camera movement you may suffer the 'strobing' effect.

An on-camera light is also an excellent solution to darker environments (beware of burning out the whites by getting too close during dancing).

I generally second what Rob said except that, in the region where I work, nobody wants video lights at their receptions and all of the venues for ceremonies forbid video lights. Another trick I've used is switching to recording in 24F rather than 60i. The slower speed means more time to acquire light. Reducing shutter speed and using 24F as the recording format also gets you the "film look" with the shooting restrictions that entails. Basically, what it entails is shooting full wide on the zoom (because the as you zoom-in the camera loses the ability to use the widest apertures) and tracking (moving side-to side with your subjects) rather than panning the camera. You want to use manual focus rather than auto-focus because really dark areas can confuse the autofocus to where it "hunts" and goes in and out of focus.

The Neat video plug in seems to be highly thought of, as you will discover if you do a search of these forums. There are versions for CS4/5, FCP, Vegas, PInnacle Studio and probably several other NLEs. Neat also makes a similar plug-in for Photoshop, so be sure you look for the Neat video plug-in rather than just the Neat Noise Reduction. There is a demo version that you can download to test out. I downloaded the demo several months ago but all the weddings I've shot this summer have had good natural lighting, so I have not yet had time to test it.

Although white light may disrupt a reception. I have had luck using colour washes bounced off of walls and ceilings. It just looks like decor but ups the general light level.
Another one is softpoint light on the podium if they use one. The wedding party table is usually enhanced with more light.

This is getting almost beyond the department of the videographer and into set dec. but it does produce good results.

I have never used a cameramount light and never intend to. It seems rather invasive. I prefer being very candid and fitting into the crowd, always looking like the camera is rolling and getting people used to it and to me as another friend in the crowd.
People also get used to the brighter lights. Especially if they are already set before the guests arrive.

Neat Video is a great crutch, buy it, but try not to depend on it. It can remove the noise but the detail won't be there that you could have gotten with better camera settings and using the best lighting you can get away with. Also your computer will spend hours processing Neat Video.

Just a few watts of soft light on the camera can make a big difference and still not blind people. The lower shutter speed is good for many situations provided the artifacts are acceptable. Just be sure the client understands the options and limitations on video in a low light venue. As noted by other, Neat Video can help in many circumstances but is not a cure all.

The trick is to deliver something that is better than the client expects.

You have been given a lot of good information here and i'm sure it will help a great deal.Shooting 30 or 24F will certainly give you more light tahn 60I. I find 24F to extreme in some cases and tend to stick with 30 frames if I need more light. I would also suggest getting to know the camera more before accepting to many gigs with it. Its better to pioneer the process when the stakes arent as high.